Air conditioning not working properly?

Air conditioning blows well and will switch to all settings such as upper, lower, defrost. However, when it's cold outside the air is cold and when it's hot outside the air is hot. On cold days the air does not warm up when the engine heats up. I tried replacing the ac control panel with two different options, but they didn't change anything. It seems like there is a good vacuum with the hoses as well.